Electroluminescent devices with improved electrical contacts



Oct. 13, 1964 R, M RULON ETAL 3,153,167

ELECTROLUMINESCENT DEVICES WITH IMPROVED ELECTRICAL CONTACTS Filed Aug. l0, 1960 vll/lill JOSEPH M. HARRls WILLIAM H. MORGAN,JR. g RICHARD RQLON ORS United States Patent O This invention relates to improvements in electroluminescent devices. More specifically, this invention relates to such devices having improved electrical contacts. Further, this invention relates to an electrical contact for use in an electroluminescent device having two electrodes, said electrical contact being rigidly andpermanently aixed to one of the electrodes and in electrical conducting relation with the other of the electrodes, but substantially insulated from said one electrode.

An electroluminescent device generally has a first electrode, a second electrode and a layer of light producing material including an electroluminescent phosphor between the first electrode and the second electrode. In practice, one of the electrodes serves as a backing piece and is usually prepared of a material which will impart stability and rigidity to the lamp. Generally, a metal plate is used; however, other materials such as glass which is adapted to conduct electricity may be substituted for the metal.

The other electrode can be a light-transmitting material. Generally when using an inorganic light-producing layer it is a transparent film of tin oxide. This electrode may be deposited, for example, by brushing or spraying the lamp with a solution of the tin chloride in a suitable organic carrier, eg., formaldehyde. Although this is the preferred embodiment of the second electrode, it may also be, for example, a piece of conductive plastic, glass or transparent fibre.

The light producing material between each of the elec- V trodes must contain an electroluminescent phosphor, for

example, zinc sulfide. The phosphor can be embedded in a solid dielectric material, for example, a glass or plastic.

It is desirable in these electroluminescent devices that the phosphor be sealed from penetration by the ambient atmosphere, since a small pinhole in the sealing can eventually cause deterioration of the phosphor due to the action of humidity and chemicals. In order to obtain etilcient sealing from moisture, it has been found desirable to fuse a layer of glass over the entire lamp surface, in many cases.

In prior devices, it has been general practice to attach electrical contacts toeach of the first and second electrodes. In processes now used, the axing of the electrical contact to the electrode which forms the backing does not present any extreme problem. If the backing is metal, the wires maybe soldered to it quite easily. The problem in fabrication lies chiefly in devising a means to affix the electrical contact to the light-transmitting electrode. When a layer of tin oxide serves as this electrode, it is apparent that the electrical contact may not be permanently soldered. Means of aiiixing have included in the past an eyelet or rivet inserted through a grommet type of insulation or ribbon held by jigs, fixtures or adhesives. It has been found that none of these contacts were completely adequate in that they were, among other things, difficult to install or lacked permanence.

It has now been discovered that the electrical contact element can be rigidly and permanently affixed to the lamp in such a manner that the entire lamp, including the contact, will be sealed from the atmosphere. According to the invention, an electrical contact element is inserted in an aperture in the lamp. This aperture usually passes through the first electrode, the second electrode and the layer of phosphor; but, if desired, the electrical contact can pass through only one of the electrodes. The unitary electrical contact element is divided in function into two portions, a shank portion and conductional portion. The shank portion is inserted in the aperture and is rigidly aiiixed to at least the backing which forms the first electrode by means of a fused glass bead. The conductional portion serves as the electrical connection between the shank portion and the light-transmitting electrode.

It is an object of our invention to provide a permanently positioned metal electrical contact element in the lamp structure.

Another object of our invention is to provide an electrical contact which is sealed from the atmosphere.

A feature of our invention is that the metal contact is an integral, rigidly affixed part of the lamp structure.

Another feature of this invention is that the contact is permanently affixed to the completed lamp and may be inserted rather easily in the fabrication operation.

Other objects, features and advantages will become apparent to those skilled in the art upon reading the following specification when taken in conjunction with the appended drawings. A

FIGURE l is a view of a typical electroluminescent device. Many shapes are possible other than that shown, for example, round or square.

FIGURE 2 of the drawing is a cross-sectional view taken along the lines 2 2 of FIGURE 1. This figure is illustrative of a species of this invention.

FIGURE 3 of the drawing is across-sectional view taken along the lines 3 3 of FIGURE 1. This ligure is illustrative of another species of this invention.

Referring now to FIGURE 2 of the drawing, a small portion 2 of the lamp is shown in enlarged detail. The backing surface 4 may be metal or glass depending upon the desired use of the lamp. In a metal lamp, the ground coat 11 adheres to the backing surface 4 and serves as a bonding surface for the phosphor coat 5. The combination of the backing surface 4 and the ground coat 11 serves as one electrode for the lamp. It is to be noted that the use of the ground coat in this first electrode is merely preferred and may be omitted, depending upon the iature of the backing surface 4 or the intended use of the amp.

The coat 5 is a light-producing material including an electroluminescent phosphor. This material usually is a combination of a fusible glass such as is shown in a copending application, Ser. No. 365,617, filed July 2, 1953, now abandoned, by R. M. Rulon. The phosphor can be, for example, copper-activated zinc sulfide such as shown in the Goldberg et al. application entitled Electroluminescent Device, Ser. No. 714,481, filed February 1l, 1958, now Patent No. 3,050,655.

Above the phosphor is an electrically conductive film 6 of light-transmitting material which will serve as the other or second electrode for the lamp. As will be noted in FIG. 2, both the peripheral edge and the annular portion surrounding the aperture of this layer are slightly recessed from the imaginary vertical extension of these respective peripheries in the lamp. These recesses are provided to inhibit the short circuiting of the lamp when in operation, which would be caused by the light-transmitting electrode touching the other electrode.

Over the entire lamp is a layer of atransparent glass 7 which serves to protect the conductive transparent film layer 6 and the phosphor coat 5 from accidental removal. As will be seen, this coat of glass completely covers not only the conductive ilm coat but also the conductional portion of the electrical contact. By this complete covering, an excellent seal is obtained which protects the phosphor coat from the atmosphere; furthermore, the stability `the same as described in FIG. 2 above.

o .a of the placement of the electrical Contact in the aperture -is insured.

The electrical contact element is comprised of two portions, the shank portion 9 and the conductional portion 8. The shank extends through the aperture in the lamp and -serves to 'connect the source of A.C. current (not shown) to the conductional `portion 8 which is in contact with t. e conductive lm. In general practice, this electrical contact is of unitary construction, generally taking the shape of a thumbtack.

The preferred composition of the electrical contact element is copper-steel or ferrous steel alloy. The diameter of the plate which forms the conductional portion is about 0.250 to 0.500 inch and has a thickness of 0.005 to 0.015 inch. The shank portion may be between 0.0027 to 0.006 inch; however, it .must be suiliciently small that it will t into the internal bore of the glass bead 10. Generally, the shank portion 9 will be 0.003 to 0.000 inch smaller than vthe bore of the bead. The shank portion 9 may be of any convenient length so long as electrical contact with the source of electricity may be made when it is positioned in the lamp.

The glass Abead 10 is composed of glass powder which has been pressed into a mold and treated to sinter and compact the powders. In the preferred embodiment this glass bead has a shank .diameter of 0.060 to 0.100 inch and a diameter at the collar of 0.020 to 0.040 inch larger than the shank. The bore'diarneter is generally 0.030 to 0.060 inch. The length of the shank generally is 0.060 to 0.100 inch andfthe height of the collar is about 0.010 to 0.030 inch. The glass bead must be of such composition that it will fuse at a temperature lower than the other glass layers ofthe lamp. When using a glaze which fuses about 1200 F., it'has been found desirable to use a glass Vbead which fuses at about 825 F.

f In the preparation of thelamp the coats 11, 5 and 6 are laid down successively -with a Afliring operation between each coating step to fuse the respective layers 11 and 5. In a separate operation, the shank yportion of the electrical contact is inserted in the bore of the glass bead. A small amount of silver containing `paste is then placed around 'fthe aperture in thelamp. This silver paste will add to the `paste mixture. The same ring serves tointegrally fuse the contact element'to the lampstructure by means of the glass bead. If it is desired to eliminate the glaze coat 7, the assembled lamp without the coat may be subjected to a heattreatmentt wherebythe electrical contact will become permanently positioned in thelamp.

Referring now to FIG. 3 of the drawing, the basic construction of the electroluminescent device is substantially The fabrication steps, however, are varied to suit this particular type of electrical contact.

As will be seen on the drawing, the electrical Contact comprises the shank portion 12 and the conductional portion 13. The glass bead 20 is fused to the backing plate 14 and to the shank portion 12 of the electrical contact element.

In the fabricatiotn of the lampi a glass bead, which is substantially identical to' that noted in the description of FIG. 1, is used. The method of establishing electrical contact between the shank and the conductive film 17 is quite different, however. In this case the shank portion 12 is inserted into the glass bead 20. The shank portion 1.2 may extend below the lower end of the glass bead and the conductional portion 13 extends about 0.010 to 0.030 inch beyond the large diameter end. With regard to the shank portion, it is essential that it be long enough that electrical contact be made with a source of electricity. The assembly is then placed in a jig or mold and heated in an oven so as to fuse the bead to the shank portion without any significant distortion.

The beaded electrical contact is inserted into the aperture of the first electrode 14 and the entire assembly coated in the conventional manner with the ground coat 15, the phosphor coat 16 and the conductive lm coat 17. After each of the coating operations, laying` down coats 15 and 16, the device is fired to fuse the respective layers. During these successive irings the bead 20 fuses and becornes firmly bonded to at least the base plate Y1401? the lamp structure.

The conductive film is removed from all of the exposed ymetal surfaces as recited in the description or" FIGURE l above. In addition, each of the coatings 1S, 16 and 17 is generally removed from the upper surface of the conductional position of the electrical Contact element. Also, there is generally removed a suicient amount of exposed metal of the conductional portion 13 so that it is reasonably iiush or coplanar with the adjacent area of the coatings. This may be done by abrasion, e.g., a file, line sand blasting tool or grinding.

The silver paste layer 18 is then applied over a portion of the conductive film layer 17 and the conductional portion 13. After the paste is thoroughly dried, the glass glaze coat 19 is applied to the devices over not only the conductive hlm layer 17, but also the silver paste layer 13 and what may remain after the abrasion step of conductional portion 13. This coat 19 is then fused in a furnace and the entire lamp is thereby sealed from the atmosphere. If it is desired to eliminate the glaze coat 19 the assembled lamp Without the coat is subjected to a heat treatment whereby the electrical contact will become permanently positioned in the device.

In each of these species of the invention recited above, it is important to note that the upper end of the Contact is substantially flush with the rest of the lamp and is an integral part thereof after the application of the glaze coat. This is a Yhighly advantageous feature since prior art contacts, which utilized an aperture in kthe-lamp, were merely removable inserts in the lamp and generally were fabricated so that the top thereof was at a higher elevation than the lamp surface.

The advantageous use of these contacts producing a relatively lat surfaced lamp is shown in FIGURE l of the drawing where each of the contacts 2 and 3 are shown. As will be seen, the invention may be constructed so that there are no elevated or exposed contacts on the upper surface of the lamp and the entire contact is an integral part thereof.

It is apparenty that modifications to the instant invention may be made by those skilled in the art. The shank portion of the electrical contact elements vmay be either tubular or solid. The abutting portion of the contact element illustrated in FIG. 1 need not be round but may be, for example, rectangular or elliptical.

Other modifications and changes will become apparent to those skilled in the art.

What we claim is:

1. An electroluminescent device comprising means forming a first electrode, means forming a second electrode, at least one of said electrodes being light transmitting, a layer of light producing material including an electroluminescent phosphor between said first and second electrode means, means forming an aperture through said device, means positioned' in said aperture to conduct electricity to one of said electrodes, sm'd conducting means comprising a shank portion and a conductional portion, ceramic means rigidly and permanently fusing said shank portion to the other of said electrodes, but substantially insulating it therefrom.

2. An electroluminescent device comprising means forming a irst electrode, means forming a second electrode, at least one of said electrodes being light transmitting, a layer of light producing material including an electroluminescent phosphor between said rst and second electrodes, means forming an aperture through said device, means positioned in said aperture to conduct electricity to one of said electrodes, said conducting means comprising a shank portion and a conductional portion, means rigidly and permanently afIiXing said shank portion to the other of said electrodes, but substantially insulating it therefrom, said means for aflxing comprising a glass bead fused to at least lsaid iirst electrode and the shank portion of said electrical contact element.

3. An electroluminescent device comprising means forming a rst electrode, means forming a second electrode, a layer of light producing material including an electroluminescent phosphor between said first and second electrodes, said second electrode being light transmitting, said first electrode comprising a metal plate, means forming an aperture through said device, means positioned in said aperture to conduct electricity to said second electrode, said means comprising a shank portion and a conductional portion, means rigidly and permanently afxing said shank portion to at least said lirst electrode but substantially insulating it therefrom, said means comprising a fused glass bead.

4. The device according to claim 3 wherein a layer of transparent glass is fused over the second electrodeV and the electrical contact element.

5. An electroluminescent device comprising means forming a first electrode, means forming a second electrode, at least said second electrode means being light transmitting, a layer of light producing material including an electroluminescent phosphor between said rst and second electrode means, means forming an aperture in at least said rst electrode, means positioned in said aperture to conduct electricity to said second electrode, said conducting means comprising a shank portion and a conductional portion, ceramic means rigidly and permanently aixing said shank portion to at least said first electrode, but substantially insulating it therefrom.

6. An electroluminescent device comprising a first electrode, a second electrode, a layer of light producing material including an electroluminescent phosphor between said irst and second electrode, at least one of said electrodes being light transmitting,` means forming an aperture through said device, an electrical contact element in said aperture, said electrical contact comprising a shank portion and a conductional portion, said conductional portion being a relatively at plate of metal of substantially greater diameter than said shank portion and being in electrical conducting relation with one of said electrodes, ceramic means rigidly and permanently aixing said shank portion to at least therother of said electrodes but substantially insulating it therefrom.

7. The device according to claim 5 wherein a layer of transparent glass is fused over the light transmitting electrode and the electrical contact element.

8. The device according to claim 7 wherein a layer of transparent glass is fused over the second electrode and the electrical contact element.V

References Cited in the le of this patent t UNITED STATES PATENTS 2,755,406 Burns July 17, 1956 2,876,374 Riggen Mar. 3, 1 959 2,900,271 MacIntyre Aug. 18, 1959 

1. AN ELECTROLUMINESCENT DEVICE COMPRISING MEANS FORMING A FIRST ELECTRODE, MEANS FORMING A SECOND ELECTRODE, AT LEAST ONE OF SAID ELECTRODES BEING LIGHT TRANSMITTING, A LAYER OF LIGHT PRODUCING MATERIAL INCLUDING AN ELECTROLUMINESCENT PHOSPHOR BETWEEN SAID FIRST AND SECOND ELECTRODE MEANS, MEANS FORMING AN APERTURE THROUGH SAID DEVICE,MEANS POSITIONED IN SAID APERTURE TO CONDUCT 